Early Morning Weather May 31, 2013

A code orange air quality alert has again been issued for much of the D.C. area.

The Air Quality Index (AQI) measures the amount of pollutants in the air from 0 to 500, designating one of six colors to the results. The higher the number, the more polluted the air is, AIRNow.gov explains.

In this case, code orange means the air may be unhealthy to sensitive groups. Those with respiratory/heart ailments, older adults and children should avoid prolonged or strenuous outdoor activity.

The color codes range from green to maroon.

Friday marks day three of a five-day heatwave. The stagnant air produced by the high pressure system creates higher levels of air pollutants. But every hot day won't produce an air quality alert, Storm Team4 meteorologist Amelia Segal says.